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DATA REPOSITORY ITEM __

ACCOMPANYING Webb et al., 2007, “Debris flows on the

Colorado Plateau: The influence of clay mineralogy and chemistry”

Data describing fine-grained sedimentary rocks and Holocene

debris flows on the Colorado Plateau

INTRODUCTION

Debris flow is a mass-wasting process that commonly occurs in numerous small

drainages on the Colorado Plateau (Woolley, 1946; Radbrunch-Hall et al., 1976; Cooley et al.,

1977; Hereford et al., 1998; Elliott and Hammack, 1999; Brabb et al., 1999; Griffiths et al.,

2004; Webb et al., 2004). They also occur in adjacent arid and semiarid regions (Blackwelder,

1928; Hammack and Wohl, 1996; Larsen et al., 2004) and worldwide (e.g., Israel; David-Novak

et al., 2004). Griffiths (1995) and Rudd (2005) hypothesized that debris-flow occurrence was

related to the co-occurrence of fine-grained bedrock bearing single-layer clays, such as illite and

kaolinite, with steep topography. This data repository provides basic data needed to test that

hypothesis for the Colorado Plateau.

This data repository is for information on regional debris-flow occurrence in watersheds

of the Colorado Plateau not affected by severe disturbances such as fire, which can greatly

increase debris-flow frequency (Wells, 1987; Wells et al., 1987; Wohl and Pearthree, 1991;

Meyer et al., 1995; Meyer and Wells, 1997). We begin with a list of fine-grained bedrock units

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on the Colorado Plateau, followed by a discussion of observational evidence for Holocene debris

flows and determination of clay mineralogy and major-cation chemistry of those units that

produce Holocene debris flows.

DEFINITION AND CLASSIFICATION OF FINE-GRAINED SEDIMENTARY ROCK

For this study, 85 mapped bedrock units containing substantial beds of fine-grained

sediment were identified on the Colorado Plateau (Table DR1). Beds are considered substantial

if they are least 1-3 m thick and composed primarily of silt and clay. These beds generally are

argillaceous and classified as shales, mudstones, siltstones, or claystones. Units containing

thinner beds or discontinuous lenses of fine-grained sediment were not included.

Rock units were defined primarily by consulting 1° x 2° geologic maps at a scale of

1:250,000 scale (exception: Salt Lake City quad at 1:125,000) – the only geologic data mapped

at a consistent scale on the Colorado Plateau (Fig. DR-1). Geologic maps at this scale were not

available for approximately 25% of the plateau along the southern and southwestern borders, and

so these areas were not evaluated. We evaluated Grand Canyon and vicinity – an important area

with a high frequency of debris-flow occurrence (Webb et al., 2000) – using three 30’ x 60’

maps (scale of 1:100,000) and one map at a scale of 1:62,500. Other maps providing important

small-scale geologic information include Huntoon et al. (1982) and Weiss et al. (1990). An index

of the geologic maps used to identify fine-grained bedrock are shown in Figure DR1.

DEBRIS FLOWS AND MASS WASTING ON THE COLORADO PLATEAU

Many mass-wasting processes transport coarse-grained sediments on the Colorado

Plateau, including landslides (Strahler, 1940; Grater, 1945; Schroder, 1971; Harty, 1991),

rockfall (Schumm and Chorley, 1964, 1966; Hereford and Huntoon, 1990), rotational slumps

(Reiche, 1937; Huntoon, 1982; Hereford and Huntoon, 1990), as well as debris flow. Pleistocene

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debris-flow deposits are commonly observed, particularly as runout facies of landslides (Fuller et

al., 1981). Coarse-grained debris flows lacking significant clay content travel only short

distances from source areas and are common in steep terrain, contributing to colluvial storage.

We restrict our discussion to Holocene debris flows initiated from shallow slope failures

during intense rainfall or, rarely, long-duration warm winter storms. Debris flows that are

mobilized from deep-seated landslides or saturated colluvium (Reneau and Dietrich, 1987;

Iverson et al., 1997) do not commonly occur under Holocene climatic conditions on the Colorado

Plateau, although such debris flows have occurred along the western side of the Wasatch Front

during years with prolonged and intense winter rainfall or rapid snowmelt (Brabb et al., 1989), as

part of landsliding in Zion Canyon (Coalpits Wash; Wayne Hamilton, pers. commun., 2006), as

well as along the Straight Cliffs on the east side of the Kaiparowits Plateau (Williams, 1984;

Boison and Patton, 1985).

Webb et al. (2000) and Griffiths et al. (2004) report three primary mechanisms of debris-

flow initiation, all involving intense or prolonged precipitation and slope failure. Failures of

colluvium, either by undercutting along channel margins or via the impact force of water pouring

over cliffs (e.g., the “firehose” effect of Johnson and Rodine, 1984), create the most frequent

debris flows in Grand Canyon; the firehose effect is also important in Canyon of Lodore along

the Green River north of the Colorado Plateau (Larsen, 2003). Direct failure of bedrock is

relatively uncommon but can generate large debris flows (Webb et al., 1988), and some notable

debris flows involve a combination of colluvial and bedrock failures (Cooley et al., 1977). Fine-

grained bedrock, particularly units containing significant amounts of single-layer clays, such as

illite and kaolinite, have been implicated in debris-flow initiation in the region. The purpose of

this data repository is to provide supporting data documentation for Webb et al. (2007).

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In Table DR-2, we provide observational evidence of strata on the Colorado Plateau and

whether or not they produce Holocene debris flows. We examined every reference to mass

wasting on the Plateau that we could find. Some erstwhile references (e.g., Realmuto, 1985;

Cardinali et al., 1990) discuss landslides and landslide deposits on the Plateau but do not mention

the occurrence of debris flows in this region. Much of the information was obtained by personal

observation in the field, primarily by driving, hiking, or boating to prominent outcrops of the

geologic unit in question and evaluating whether or not it produced Holocene debris flows.

Each fine-grained bedrock unit is classified as a source of Holocene debris flows

(producer), not a source of Holocene debris flows (non-producer), or an unknown contributor to

debris flows (Table DR-2). We considered a fine-grained sedimentary unit to be a debris-flow

producer if (1) historical debris flows could be traced to the unit, (2) debris flows of

demonstrable Holocene age could be traced to the unit, or (3) previous studies have indicated

that the unit produced Holocene debris flows. We consider only Holocene debris flows that

originate as shallow slope failures in colluvium or weathered bedrock during intense

precipitation (Griffiths et al., 2004). We do not consider debris flows that originate as landslides

or debris slides resulting from gradual saturation and increased pore-pressure in underlying soil,

colluvium, or shales, a common mechanism in may parts of the Colorado Plateau, such as on the

Wasatch Front (Jeppson, 1985; Wieczorek et al., 1989), the eastern side of the Kaiparowits

Plateau (Williams, 1984), and other parts of the Colorado Plateau (Brabb et al., 1999).

CLAY MINERALOGY AND MAJOR-CATION CONCENTRATIONS

As discussed in Webb et al. (2007), we measured clay mineralogy and major-cation

concentrations for 59 samples from 52 units (Table DR3). Mineralogy of the debris-flow

deposits, colluvium, and bedrock was determined through semi-quantitative X-ray diffraction

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analyses of clay-size fractions (Starkey et al., 1984). Minerals identified include the clay mineral

groups kaolinite, illite, smectite, as well as quartz, carbonate, and other trace minerals in percent

by weight with an overall error range of ±20% (S.J. Sutley, U.S. Geological Survey, written

commun., 2006). The concentrations of soluble Na+, K+, Mg++, and Ca++ of the clay-size fraction

were determined using an ammonium acetate extract and analysis using an inductively coupled

plasma mass spectrometer (ICP-MS) and are expressed in units of μg/g. The uncertainty of these

analyses is ±10% of the mean (A. Ray-Maitra, University of Arizona, written commun., 2006).

Finally, we collected samples from fine-grained rock units known to produce Holocene

debris flows (Griffiths et al., 2004; Webb et al., 2004), colluvial deposits topographically lower

than these bedrock units, and debris-flow deposits. A total of 8 fine-grained bedrock units

produce debris flows in Grand Canyon; similarly, 5 units produce debris flows in Cataract

Canyon and vicinity (Table DR-4). We collected 17 and 16 samples of colluvium and 14 and 12

samples of debris-flow deposits from Grand and Cataract Canyons, respectively (Table DR-4).

Samples of colluvium and debris-flow deposits were extracted from < 2 mm samples for major-

cation analysis and < 63 μ samples for clay-mineralogy analysis obtained from <32 mm diameter

matrix samples.

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Williams, P.L., 1964, Geology, structure, and uranium deposits of the Moab quadrangle,

Colorado and Utah: U.S. Geological Survey Miscellaneous Geologic Investigations Map

I-360, scale 1:250,000, 1 sheet.

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Williams, P.E., and Hackman, R.J., 1971, Geology of the Salina quadrangle, Utah: U.S.

Geological Survey Miscellaneous Geologic Investigations Map I-591-A, scale 1:250,000,

1 sheet.

Williams, V.S., 1984, Pedimentation versus debris-flow origin of plateau-side desert terraces in

southern Utah: Journal of Geology, v. 92, p. 457-468.

Wilson, R.F., 1967, Whitmore Point, a new member of the Moenave Formation in Utah and

Arizona: Plateau, v. 40, no. 1, p. 29-40.

Witkind, I.J., 1995, Geologic map of the Price 1° x 2° quadrangle, Utah: U.S. Geological Survey

Miscellaneous Investigations Series Map I-2462, scale 1:250,000, 1 sheet.

Wohl, E.E., and Pearthree, P.A., 1991, Debris flows as geomorphic agents in the Huachuca

Mountains of southeastern Arizona: Geomorphology, v. 4, p. 273-292.

Woolley, R.R., 1946, Cloudburst floods in Utah, 1850-1938: U.S. Geological Survey Water-

Supply Paper 994, 128 p.

Young, R.G., 1982, Stratigraphy and petroleum geology of the Mesaverde Group, southeastern

Piceance Creek Basin, Colorado, in Averett, W.R. (editor), Southeastern Piceance Basin,

western Colorado: Grand Junction, Colorado, Great Western Printing, p. 45-54.

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TABLE DR1. BEDROCK UNITS ON THE COLORADO PLATEAU THAT CONTAIN

SIGNIFICANT FINE-GRAINED SEDIMENTARY LAYERS OR UNITS

Spatial Depositional Age Group Formation Member extent environment Source

CENOZOIC Tertiary Bidahochi vw lacustrine 16 San Jose Tapicitos w fluvial 29 San Jose Regina vw fluvial 29 San Jose Cuba Mesa vw fluvial 29 Nacimiento vw lacustrine 13 Animas w/m fluvial 1 Claron Pink limestone s lacustrine 20 Pine Hollow s fluvial 3 Duschene River Starr Flat vs fluvial 28 Duschene River Lapoint s fluvial 28 Duschene River Dry Gulch Creek m fluvial 28 Duschene River Brennan Basin vw fluvial 28 Uinta vw fluvial 4 Green River SS and LS facies m/w lacustrine 34 Green River Saline facies m lacustrine 34 Green River Upper / Evacuation Creek vw lacustrine 34 Green River Middle / Parachute Creek vw lacustrine 34 Green River Lower / Douglas Creek w lacustrine 34 Wasatch vw fluvial 4 Colton w fluvial 30 Flagstaff s lacustrine 32 North Horn s/m fluvial 32 MESOZOIC Cretaceous Kirtland upper shale w fluvial 1 Kirtland lower shale vw fluvial 1 Fruitland w fluvial 1 Lewis m marine - deep 1 Mesaverde Menifee w/vw marine - shallow 23 Mesaverde Tuscher w marine - shallow 12 Mesaverde Hunter Canyon vw marine - shallow 21 Mesaverde Farrer w marine - shallow 12 Mesaverde Price River m fluvial 2 Mesaverde Blackhawk vs marine - shallow 10 Mesaverde Mt. Garfield w marine - shallow 9 Mesaverde Neslen m marine - shallow 12 Mesaverde Williams Fork m/w fluvial 35 Mesaverde Ohio Creek vw fluvial 7 Mesaverde Iles m marine - shallow 2 Mesaverde Yale Point m/w marine - shallow 24 Mesaverde Toreva Middle Carb. Mudstone m marine - shallow 24 Mancos Masuk Shale/Middle m marine - deep 4 Mancos Blue Gate m marine - deep 4 Mancos Tununk m marine - deep 4 Kaiparowits w/vw fluvial 14 Wahweap vw fluvial 24 Straight Cliffs undifferentiated vw marine - shallow 24 Tropic Shale s/m marine - deep 15 Cedar Mountain upper member m lacustrine 15 Burro Canyon w fluvial 31 Jurassic Morrison Brushy Basin vw fluvial 5 Morrison Westwater Canyon m/s fluvial 5 Morrison Recapture m/s fluvial 5 Morrison Salt Wash m/s fluvial 5 San Rafael Summerville m fluvial 31 San Rafael Wanakah s lacustrine 27 San Rafael Curtis m marine - shallow 34 San Rafael Carmel - upper w fluvial 19 San Rafael Carmel - lower w fluvial 19

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Spatial Depositional Age Group Formation Member extent environment Source Arapien Twist Gulch vs marine - shallow 32 Arapien Twelve mile Canyon m marine - shallow 32 Glen Canyon Kayenta m/w fluvial 24 Glen Canyon Moenave m/w fluvial 33 Stump m marine - shallow 28 Triassic Chinle Owl Rock vw lacustrine 8 Chinle Petrified Forest vw lacustrine 8 Chinle Sandstone and Mudstone w fluvial 8 Moenkopi upper red w marine - shallow 26 Moenkopi middle red w marine - shallow 26 Moenkopi lower red w marine - shallow 26 PALEOZOIC Permian Cutler Undifferentiated w/vw fluvial 1 Cutler Organ Rock m fluvial 1 Cutler Halgaito s/m fluvial 1 Cutler Elephant Canyon m marine - shallow 1 Hermit m fluvial 19 Supai Esplanade w fluvial 19 Park City m marine - deep 28 Madera m/s marine - shallow 6 Pennsylvanian Morgan m/w marine - shallow 17 Hermosa Honaker Trail s marine - shallow 2 Mississippian Doughnut m marine - shallow 17 Cambrian Bright Angel s/m marine -shallow 22 Lodore s marine - shallow 17 PROTEROZOIC Late Chuar Kwagunt m marine - shallow 25 Chuar Galeros s/m marine - shallow 25 Middle Unkar Dox s/m marine - shallow 25 Unkar Hakatai s marine - shallow 25

Notes: Spatial extent describes relative spatial extent on the plateau: vw, very widespread; w, widespread, m, medium extent; s, small area; vs, very small area.

References1. Baars (2000) 2. Baars (1973) 3. Berman et al. (1980) 4. Bowers (1972) 5. Cadigan (1967) 6. Cashion (1973) 7. Chronic (1987) 8. Daub (1982) 9. Dubiel (1987) 10. Erdman (1934) 11. Fisher et al. (1960) 12. Franczyk et al. (1990) 13. Gardner (1910) 14. Gregory and Moore (1931) 15. Hackman and Wyant (1973) 16. Hackman and Olson (1977) 17. Hayes and Santos (1969) 18. Haynes et al. (1972) 19. Haynes and Hackman (1978) 20. Hintze (1988) 21. Johnson and May (1978) 22. McKee (1974) 23. Molenaar (1987) 24. Morales (2003) 25. Nations and Stump (1996)

26. Phoenix (1963) 27. Ridgley (1989) 28. Rowley et al. (1985) 29. Simpson (1948) 30. Spieker (1946) 31. Williams (1964) 32. Williams and Hackman (1971) 33. Wilson (1967) 34. Witkind (1995) 35. Young (1982)

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TABLE DR2. DEBRIS-FLOW POTENTIAL OF SEDIMENTARY ROCKS ON THE COLORADO PLATEAU CONTAINING FINE-GRAINED UNITS

Unit or Formation Name

Depositional† Environment

Holocene Debris Flows‡

Older Debris Flows Reference

Bright Angel marine - s Y P.G. Griffiths, R.H. Webb, pers. observ. Chinle, Monitor Butte m. fluvial Y Y Melis et al. (1994), P.G. Griffiths, pers.

observ Colton fluvial Y P.G. Griffiths, pers. observ. Dox marine - s Y P.G. Griffiths, R.H. Webb, pers. observ. Elephant Canyon marine - s Y R.H. Webb, L.P. Rudd, pers. observ. Esplanade fluvial Y P.G. Griffiths, R.H. Webb, pers. observ. Flagstaff lacustrine Y P.G. Griffiths, pers. observ. Galeros marine - s Y P.G. Griffiths, R.H. Webb, pers. observ. Hakatai marine - s Y P.G. Griffiths, R.H. Webb, pers. observ. Halgaito fluvial Y R.H. Webb, L.P. Rudd, P.G. Griffiths, pers.

observ. Hermit fluvial Y P.G. Griffiths, R.H. Webb, pers. observ. Kwagunt marine - s Y P.G. Griffiths, R.H. Webb, pers. observ. Moenkopi, lower m. marine - s Y Y L.P. Rudd (2005) Moenkopi, upper m. marine - s Y Y L.P. Rudd (2005) Morrison, Brushy Basin m. fluvial Y Williams (1984), R.H. Webb, pers. observ. Morrison, Salt Wash SS m. fluvial Y Williams (1984), R.H. Webb, pers. observ. North Horn fluvial Y Y Brabb et al. (1989), Harty (1991), R.H.

Webb, pers. observ. Organ Rock fluvial Y R.H. Webb, L.P. Rudd, pers. observ. Straight Cliffs marine - s Y Y Williams (1984), Fuller et al. (1981), P.G.

Griffiths, pers. observ. Wanakah lacustrine Y R.H. Webb, pers. observ. Wasatch fluvial Y Y R.H. Webb, pers. observ. Animas fluvial N P.G. Griffiths, R.H. Webb, pers. observ. Arapien marine - s N P.G. Griffiths, R.H. Webb, pers. observ. Bidahochi lacustrine N Y P.G. Griffiths, R.H. Webb pers. observ. Chinle, Petrified Forest m. lacustrine N Y P.G. Griffiths, pers. observ. Fruitland fluvial N P.G. Griffiths, R.H. Webb, pers. observ. Green River, SS/LS m. lacustrine N P.G. Griffiths, pers. observ Green River, middle m. lacustrine N P.G. Griffiths, pers. observ Green River, upper m. lacustrine N P.G. Griffiths, pers. observ. Honaker Trail marine - s N P.G. Griffiths, R.H. Webb, pers. observ. Kayenta fluvial N L.P. Rudd, pers. observ. Kirtland fluvial N P.G. Griffiths, R.H. Webb, pers. observ. Lewis marine - d N P.G. Griffiths, R.H. Webb, pers. observ. Mancos marine - d N L.P. Rudd, R.H. Webb, pers. observ. Nacimiento lacustrine N P.G. Griffiths, R.H. Webb, pers. observ. Park City marine - d N P.G. Griffiths, L.P. Rudd, pers. observ. San Jose fluvial N P.G. Griffiths, R.H. Webb, pers. observ. Tropic marine - d N P.G. Griffiths, pers. observ. Carmel fluvial I Cedar Mountain lacustrine I

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Unit or Formation Name

Depositional† Environment

Holocene Debris Flows‡

Older Debris Flows Reference

Claron lacustrine I Curtis marine - s I Cutler, undifferentiated fluvial I Y Duschene River fluvial I Farrer marine - s I Kaiparowits fluvial I Y Moenave fluvial I Stump marine - s I Summerville fluvial I Tuscher marine - s I Uinta fluvial I Wahweap fluvial I Y

† Depositional environments, marine – d, deep marine; marine – s, shallow marine ‡ Y, Holocene debris flows occur; N, Holocene debris flows do not occur; I, indeterminate whether or not Holocene debris flows occur. Holocene debris flows are defined as debris flows initiated by intense rainfall and excludes landslides caused by gradual saturation of source material.

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TABLE DR3. BEDROCK UNITS ON THE COLORADO PLATEAU SAMPLED FOR CLAY MINERALOGY AND MAJOR CATION CONCENTRATION

CLAY MINERALOGY (weight %) MAJOR CATIONS (μg/g)

Formation Member Illite Kao-linite

Mont-moril-lonite Quartz

Carb-onate Other Ca Na Mg K

UNITS THAT PRODUCE HOLOCENE DEBRIS FLOWS (n = 21) Bright Angel 68 22 0 3 0 7 57 6 26 11 Chinle Monitor Butte 32 44 7 7 0 10 2 85 7 6 Colton 35 37 7 11 0 10 30 29 39 2 Dox 65 14 0 8 0 13 39 31 20 10 Elephant Canyon† 28 25 0 15 7 25 15 39 5 7 Esplanade 50 40 2 3 5 0 44 35 19 3 Flagstaff Flagstaff Limestone 21 30 4 12 11 22 29 42 27 2 Galeros† 36 35 3 8 8 11 36 38 23 2 Hakatai 52 15 2 12 0 19 50 10 36 4 Halgaito† 59 30 0 5 1 6 42 9 9 10 Hermit 54 41 0 0 0 5 47 10 25 18 Kwagunt† 53 8 3 10 0 26 24 15 40 21 Moenkopi Lower 66 22 0 11 0 1 27 18 36 19 Moenkopi Upper 40 42 3 9 2 4 36 35 23 6 Morrison Brushy Basin 55 4 0 12 0 29 25 26 45 4 Morrison Salt Wash Sandstone 60 11 0 15 5 9 19 53 27 1 North Horn† 14 44 20 8 1 15 7 53 3 36 Organ Rock 38 52 0 2 0 8 21 32 22 26 Straight Cliffs 8 26 60 4 0 2 10 40 44 6 Wanakah 31 20 0 11 14 24 76 1 20 4 Wasatch 50 4 0 8 5 33 12 64 21 3

Average 44 27 5 8 3 13 31 32 25 10 Standard deviation 17 14 13 4 4 10 18 21 12 9

UNITS THAT DO NOT PRODUCE HOLOCENE DEBRIS FLOWS (n = 17) Animas 1 4 91 0 1 3 40 52 8 0 Arapien Unit D 51 10 2 4 8 25 90 2 5 2 Bidahochi 22 6 65 2 2 3 5 89 3 3 Chinle Petrified Forest 41 11 42 3 0 3 2 98 0 0 Fruitland 0 5 15 30 0 50 56 15 28 0 Green River Middle 20 11 27 6 13 23 43 33 23 1 Green River Upper 4 1 53 3 16 23 62 30 7 1 Green River Sandstone/Limestone 4 1 87 2 3 3 22 70 7 1 Honaker Trail† undifferentiated 9 10 46 5 2 29 39 23 16 9 Kayenta 45 7 31 10 0 7 49 27 24 1 Kirtland Upper 0 2 92 4 0 2 19 77 4 0 Lewis 10 15 20 35 5 15 0 50 50 0 Mancos 20 34 7 13 5 21 12 87 1 0 Nacimiento 0 10 90 0 0 0 1 98 0 0 Park City 2 1 69 1 5 22 13 38 41 8 San Jose undifferentiated 6 10 74 2 6 2 7 88 4 1 Tropic 16 19 57 2 6 0 15 82 2 0

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CLAY MINERALOGY (weight %) MAJOR CATIONS (μg/g)

Formation Member Illite Kao-linite

Mont-moril-lonite Quartz

Carb-onate Other Ca Na Mg K

Average 15 9 51 7 4 14 27 57 13 2 Standard deviation 17 8 30 10 5 15 25 31 15 3

UNITS WITH INDETERMINATE DEBRIS-FLOW STATUS (n = 14) Carmel 10 3 47 6 21 13 26 34 40 0 Cedar Mountain 0 0 75 13 0 12 7 88 4 1 Claron 5 56 0 5 32 2 62 13 19 6 Curtis 6 0 9 13 46 26 26 48 19 7 Cutler Undifferentiated 55 18 0 13 0 14 18 66 14 2 Duschene River Brennan Basin 12 10 18 14 27 19 7 74 18 1 Farrer 9 23 0 33 0 36 17 14 68 1 Kaiparowits 6 15 54 7 1 17 15 79 5 0 Moenave 62 24 0 10 0 4 44 20 32 4 Stump 13 0 52 4 19 12 29 39 27 5 Summerville 5 0 38 14 15 28 34 58 8 1 Tuscher 25 26 39 6 0 4 0 95 0 4 Uinta Upper 7 5 70 11 2 5 27 60 11 2 Wahweap 5 30 2 27 16 20 22 61 11 7

Average 16 15 29 13 13 15 24 53 20 3 Standard deviation 19 16 28 8 15 10 16 27 18 2

† Values are the average of two to three samples.

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TABLE DR4. CLAY MINERALOGY OF COLLUVIUM AND DEBRIS-FLOW DEPOSITS SAMPLED FROM THE COLORADO PLATEAU

CLAY MINERALOGY (weight %) MAJOR CATIONS (μg/g)

Sample Number Location Illite Kaolinite K+I† Montmorillonite Quartz

Carb- onate Other Total Other‡

Colluvium Carcass-2 50-Mile Bench 24 11 35 60 2 0 3 5 Sooner-1 50-Mile Bench 20 14 34 60 5 1 0 6 CC210.7R-2 Cataract Canyon 24 44 68 0 9 1 22 32 CC212.0L-1 Cataract Canyon 24 40 64 0 12 1 23 36 CC212.3R-1 Cataract Canyon 33 45 78 4 4 2 12 18 CC213.0L-1 Cataract Canyon 24 48 71 0 6 1 21 29 CC202.2L-1 Cataract Canyon 23 37 60 21 6 0 13 20 970325-1 Cataract Canyon 14 61 75 0 7 8 10 25 940328-3 Cataract Canyon 24 48 72 0 6 1 21 28 940328-1 Cataract Canyon 33 45 78 4 4 2 12 18 940328-2 Cataract Canyon 24 40 64 0 12 1 23 36 940329-1 Cataract Canyon 24 44 68 0 9 1 22 32 010530-10 Cataract Canyon 7 16 23 31 11 24 11 46 970327-1 Cataract Canyon 11 57 68 0 7 13 12 32 940401-1 Cataract Canyon 23 37 60 21 6 0 13 19 010531-3 Cataract Canyon 40 41 81 0 5 3 11 19 010531-7 Cataract Canyon 15 14 29 30 10 10 21 41 010531-8 Cataract Canyon 23 17 40 24 7 9 20 36 94-127.6L-2 Grand Canyon 45 29 74 6 10 3 7 20 94-58.0L-1 Grand Canyon 20 68 88 0 9 3 0 12 94-62.2R-3 Grand Canyon 32 35 67 7 10 9 7 26 94-62.6R-2 Grand Canyon 22 49 71 2 12 10 5 27 94-62.6R-3 Grand Canyon 32 35 67 7 10 12 4 26 95-127.6L-1 Grand Canyon 45 26 71 0 12 9 8 29 95-24.4L-1 Grand Canyon 29 62 91 0 6 3 0 9 95-62.5R-1 Grand Canyon 57 23 80 8 6 5 1 12 95-62.5R-4 Grand Canyon 43 40 83 8 5 3 1 9 95-67.2L-1 Grand Canyon 10 82 92 0 5 3 0 8 95-67.2L-2 Grand Canyon 29 63 92 0 6 2 0 8 95-68.5L-6 Grand Canyon 22 57 79 0 8 12 1 21 95-94-179.4L-3 Grand Canyon 35 29 64 6 6 15 9 30 94-63.3R-1 Grand Canyon 49 23 72 10 12 1 5 18 94-127.3L-1 Grand Canyon 44 25 69 17 9 2 3 14 95-7.9L-2 Grand Canyon 29 28 57 34 5 3 1 9 94-7.9R-1 Grand Canyon 15 15 30 60 5 1 3 9 Total average ( N = 35§) 28 38 66 12 8 5 9 22

Standard deviation 12 17 18 18 3 5 8 11 Grand Canyon average (N = 17) 33 41 73 10 8 6 3 17

Standard deviation 13 19 15 16 3 4 3 8 Cataract Canyon average (N = 16) 23 40 62 8 8 5 17 29

Standard deviation 8 13 17 12 3 7 5 9

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CLAY MINERALOGY (weight %) MAJOR CATIONS (μg/g) Sample Number Location Illite Kaolinite K+I† Montmorillonite Quartz

Carb- onate Other Total Other‡

Debris-Flow Deposits CC210.7R-1 Cataract Canyon 10 67 77 11 5 2 5 11 970324-2 Cataract Canyon 33 36 69 0 5 9 17 31 010530-1 Cataract Canyon 36 46 82 0 4 4 10 18 010529-8 Cataract Canyon 24 37 61 0 7 14 18 39 940329-2 Cataract Canyon 10 67 77 11 5 2 5 12 010530-9 Cataract Canyon 20 30 50 0 8 22 20 50 970326-2 Cataract Canyon 38 45 83 0 4 4 9 17 970327-1 Cataract Canyon 22 44 66 10 4 1 19 24 010530-17 Cataract Canyon 21 30 51 5 9 16 19 44 010531-5 Cataract Canyon 60 17 77 0 7 7 9 23 010531-6 Cataract Canyon 8 10 18 16 8 45 13 66 010601-1 Cataract Canyon 30 20 50 19 6 14 11 31 94-127.5L-1 Grand Canyon 38 38 76 0 7 14 3 24 94-62.6R-1 Grand Canyon 58 24 82 0 11 7 0 18 94-72.0R-1 Grand Canyon 48 30 78 0 7 0 15 22 94-75.5L-1 Grand Canyon 62 17 79 0 10 9 2 21 95-71.2R-3 Grand Canyon 19 31 50 0 4 1 45 50 95-98.2R-1 Grand Canyon 42 38 80 0 6 9 5 20 94-179.4L-1 Grand Canyon 36 24 60 2 13 21 4 38 95-126.9L-2 Grand Canyon 43 43 86 2 3 5 4 12 95-179.4L-24 Grand Canyon 34 38 72 4 7 15 2 24 94-224.5L-1 Grand Canyon 60 15 75 6 8 9 2 19 95-205.5L-7 Grand Canyon 56 15 71 8 14 0 7 21 95-179.4l-17 Grand Canyon 21 28 49 12 8 18 13 39 94-71.3R-1 Grand Canyon 22 26 48 39 0 0 13 13 95-0.0R-1 Grand Canyon 14 18 32 51 2 4 11 17 Total average (N = 26) 33 32 65 8 7 10 11 27

Standard deviation 15 17 12 3 10 9 14 Grand Canyon average (N = 12) 40 28 67 9 7 8 9 24

Standard deviation 9 16 16 4 7 11 11 Cataract Canyon average (N = 14) 26 37 63 6 6 12 13 31

Standard deviation 18 19 7 2 12 6 17

† Sum of kaolinite and illite concentrations. ‡ Sum of quartz, carbonate, and other concentrations. § Excludes samples from 50-Mile Bench.

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FIGURES

Figure DR1. Index map showing the geologic maps used in this study.

Figure DR2. Map showing the locations of samples of colluvium (solid circles) and debris flow

deposits (empty circles) collected along the Colorado River in Grand Canyon, Arizona. Location

is also indicated by river mile.

Figure DR3. Map showing the locations of samples of colluvium (solid circles) and debris flow

deposits (empty circles) collected along the Colorado River in Cataract Canyon, Utah. Location

is also indicated by river mile.

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